Characterization of Al-Si-Cu-Mg foams manufactured in-situ

Abstract

This work presents the characterization of Al-6Si-3Cu-xMg (x = 7, 9 and 11 wt%) foams obtained through the in-situ process. Heat treatments which consisted on over-heating the alloys during 6 h at 520, 560 and 600 °C were performed. The microstructural changes, the quantification and measurement of sizes and shapes of second phases and pores were carried out by means of Optical Microscopy (OM), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Compression tests and density measurements were also assessed. The results showed porosities ranging from 2 to 40%, with pore sizes from 20 to 150 μm, shape factors from 0.59 to 0.72, and maxima relative densities between 0.89 and 0.91. The formation of these pores was attributed to the dissolution and melting processes of the second phases and the shrinkage originated after their solidification. Fragmentation, spheroidization and coarsening of second phases during the solution heat treatment was also observed. It was found that the microstructures of the foams, including pores and second phases, strongly depended on the over-solution temperature and the Mg content. Temperature was the manufacturing variable that most affected the size and quantity of the pores produced.